1. Field of the Invention
The invention relates to a D/A converting circuit, and in particular relates to a low powered D/A converting circuit.
2. Description of the Related Art
FIG. 1 is a conventional four-bit resisting digital to analog converter (D/A converter) 100. The four-bit resisting D/A converter 100 comprises sixteen serial resistors (R1˜R16) and sixty four (4*16) switch transistors. The serial resistors are coupled between a reference voltage Vref and a ground voltage GND. As shown in FIG. 1, the four-bit resisting D/A converter 100 uses serial resistors (R1˜R16) to generate sixteen different voltages and controls turning on or off of switch transistors according to digital data (D1, D2, D3 and D4) to output different output voltages corresponding to digital data (D1, D2, D3 and D4) to output terminal 101. Though the four-bit resisting D/A converter 100 can rapidly generate different output voltages corresponding to digital data (D1, D2, D3 and D4) by using the voltage dividing method. However, resistors and switch transistor are required more for higher resolution. For example, if the converter is an eight-bit converter, the converter needs 512 serial resistors and 2048 switch transistors. The required circuit layout size is much larger than the four-bit converter. Thus, the resisting D/A converter is not suitable for high-resolution D/A converter application. In addition, a lot of power consumption is required by the resisting D/A converter.
Recently, with display panel trends of higher resolution, lower power and smaller size display panels, reduction of power consumption and circuit layout size have become more and more important.